Journal of Research in Biology

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1 Journal of Research in Biology Journal of Research in Biology An International Open Access Research Journal Original Research Anatomical variation in the olfactory apparatus of marine teleosts Authors: Biswas S 1, Datta NC 2, Sarkar SK 1 and De SK 1. Institution: 1. Department of Zoology, Vidyasagar University, Midnapore (West) , West Bengal, India /20 B. T. Road, Kolkata , West Bengal, India. Corresponding author: Subrata Kumar De. skdvu@yahoo.co.in ABSTRACT: The olfactory apparatus of marine teleosts viz., Rastrelliger kanagurta, Scomberoides commersonianus and Platycephalus scaber belonging to the family of Scombridae, Carangidae and Platycephalidae respectively has been fixed in 10% formaldehyde solution for 24 h and anatomically examined under light microscope (LM). Anatomical variation regarding the nostrils, olfactory rosette, occurrence of accessory nasal sacs, olfactory lobes, length of the olfactory nerve tracts, etc. are observed. These morphological variations may denote species specific and may decisive for several biological functions. Keywords: Olfactory, Rosette, Scombridae, Carangidae, Platycephalidae, etc. Phone No: Web Address: documents/ra0304pdf. Article Citation: Biswas S, Datta NC, Sarkar SK and De SK. Anatomical variation in the olfactory apparatus of marine teleosts. Journal of Research in Biology (2013) 3(1): Dates: Received: 08 Nov 2012 Accepted: 20 Nov 2012 Published: 09 Jan 2013 This Open Access article is governed by the Creative Commons Attribution License ( creativecommons.org/licenses/by/2.0), which gives permission for unrestricted use, noncommercial, distribution and reproduction in all medium, provided the original work is properly cited. Journal of Research in Biology An International Open Access Research Journal JRB 2013 Vol 3 No 1

2 INTRODUCTION Olfaction is an important type of chemoreception which is mediated through well developed, complex and organized olfactory system in vertebrates (Freitag et al., 1999). This system generally develops from the specialized tissue, called olfactory placode (von Kupffer, 1894). In the early stage of development, placodes are formed from the preplacodal ectoderm of the anterior region of the embryo, medial to epidermis and lateral to both neural crest and neural plate (Knouff, 1935). The developmental process leading to the formation of fish olfactory organ, is little diverse (Hansen and Zielinski, 2005). The peripheral olfactory organ is the first chemosensory organ to develop in fish preceding the systems of solitary chemosensory cells (Kotrschal et al., 1997) and taste (Hansen et al., 2003). Fish generally possesses a paired olfactory organ located at the anterior part of the head (Derivot, 1984; Hansen and Zeiske, 1998; Døving, 2003; De and Sarkar, 2009). The olfactory chambers, olfactory rosette, accessory nasal sacs, olfactory bulbs, olfactory nerve tracts and brain are the major components of fish olfactory apparatus (Hamdani and Døving, 2007). The anatomy of the olfactory apparatus shows wide range of structural diversity regarding the shape and size of the olfactory rosette, number of the olfactory lamellae, occurrence of accessory nasal sacs, etc. among the teleostean groups (Kleerekoper, 1969). The anatomical details of the olfactory apparatus in several species belonging to the diverse teleostean taxa with respect to their habitat are still an obscure part in sensory biology. The sensory systems of fishes show notable adaptations according to habitat and mode of life in comparison with the higher vertebrates (Bone and Moore, 2008). The present study focused on the true anatomy of the olfactory apparatus in three species of different ecological habitat viz., Rastrelliger kanagurta (Cuvier, 1816), a marine oceanodromous fish; Scomberoides commersonianus (Lacepede, 1801), a brackish water amphidromous fish and Platycephalus scaber (Linnaeus, 1758), an estuarine amphidromous fish to unfold their structural components and functional significance in olfaction. MATERIALS AND METHODS Adult, sex-independent specimens of R. kanagurta, S. commersonianus and P. scaber were collected from the coastal regions of Bengal, India. Specimens were preserved in 10% formaldehyde solution for 24 h and brought to the laboratory. The olfactory apparatus of these species were dissected out and separately mount on grease free slide by using glycerine. The olfactory apparatus of respective species was examined under light microscope (LM). RESULTS R. kanagurta (Figure 1A) possesses two pairs of nostril viz., anterior nostril and posterior nostril (Figure 1B). The anterior nostril is an oval shaped structure, encircled by a thick lip like ridge of skin and located at the dorsal region of the snout where as the posterior nostril is situated in front of the eye. R. kanagurta shows a slit like structure i.e., posterior nostril which is located at a moderate distance from the anterior one (Figure 1B). The olfactory apparatus of the said species is present at the antero-dorsal side of the snout in between the anterior and posterior nostril (Figure 1C). The multilamellar olfactory rosette is oval in shape and is situated at the floor of the olfactory chamber (Figures 1D and 1E). The triangular olfactory lamellae vary from 60 to 70 in number per rosette and are arranged pinnately on the raphe (Figure 1E). The accessory nasal sacs are clearly marked in the olfactory apparatus of R. kanagurta. The lacrimal sac is conical in shape and located at the antero-medial region of lachrymal bone in association with olfactory rosette (Figures 1C and 1D). The ethmoidal sac is connected at the posterior part of the olfactory rosette and situated within a groove at the antero-lateral extension of the 743 Journal of Research in Biology (2013) 3(1):

3 Plate - 1 OLR LS ETS Figure 1A - Schematic representation of Rastrelliger kanagurta. Figure1B - The diagram shows oval shaped anterior nostril and transverse slit like posterior nostrils of R. kanagurta. Figure 1C - The olfactory apparatus of R. kanagurta shows olfactory rosette (OLR), lacrimal sac (LS), ethmoidal sac (ES), olfactory nerve (OLN), olfactory lobe (OL), cerebral hemisphere (CHS), optic lobe (OPL), cerebellum (CBL), medulla oblongata (MO), etc. Figure 1D - The olfactory rosette (OLR) along with conical accessory nasal sacs viz., lacrimal sac (LS) and ethmoidal sac (ETS). Figure 1E - The dorsal view of oval shaped olfactory rosette shows central raphe (r), two rows of lamella (l). The olfactory lamella is triangular in shape with prominent dorsal end (de), proximal end (pe) and ventral margin (vm). frontal bone (Figures 1C and 1D). The olfactory nerve tracts are arised from the base of olfactory rosette and the length varies from 16 mm to 18 mm respectively. The distal part of the olfactory nerve tracts are connected with olfactory lobes of the brain. The size of the olfactory lobes is comparatively small in R. kanagurta (Figure 1C). In S. commersonianus (Figure 2A), the nostrils are closely associated. The anterior nostril is an oval shaped aperture and partly guarded by a nasal flap where as the posterior nostril is crescentric in shape (Figure 2B). The olfactory rosette is circular in shape and consisting of two pairs of olfactory lamellae (Figures 2C and 2D). The number of the olfactory lamellae ranges from 100 to 140 per rosette (Figure 2D). The accessory nasal sacs are not distinct in the olfactory apparatus. The olfactory nerve tracts are arised from the base of the olfactory rosette and the length is ranges from 10 mm to 12 mm. The olfactory lobe is comparatively large in size (Figure 2C). Interestingly, the nostrils of P. scaber (Figure 3A) are situated at the antero-dorsal region to the Journal of Research in Biology (2013) 3(1):

4 Plate - 2 Figure 2A - Schematic representation of Scomberoides commersonianus. Figure 2B - The diagram shows anterior and posterior nostrils of S. commersonianus. Nasal flap (FL) is distinct. Figure 2C - The olfactory apparatus of S. commersonianus is comprises of olfactory rosette (OLR), olfactory nerve (OLN), olfactory lobe (OL), cerebral hemisphere (CHS), optic lobe (OPL), cerebellum (CBL), medulla oblongata (MO), etc. Figure 2D - The circular olfactory rosette shows central raphe (r), two rows of lamella (l). The olfactory lamella is large, triangular in shape with prominent dorsal margin (dm), dorsal end (de), ventral margin (vm) and lingual process (lp). eye and lying far apart from each other. The anterior nostril is oval in shape and has a tongue like nasal flap where as the posterior nostril is valvular (Figure 3B). The olfactory rosette is relatively large in size and oval in shape (Figures 3C and 3D). The number of the olfactory lamellae varies from 50 to 76 in number per rosette (Figure 3D). The absence of accessory nasal sacs is noted in the olfactory apparatus of P. scaber. The length of the olfactory nerve tracts ranges from 22 mm - 24 mm. and it is well connected with the olfactory lobe of the brain (Figure 3C). DISCUSSION Olfactory systems of fish are among the most highly developed olfactory senses of vertebrates (Kleerekoper, 1969). The sense of olfaction is mediated through olfactory apparatus associated with nostrils. The nostrils are responsible for incurrent and excurrent of water during water ventilation (Nevitt, 1991). The structure of the anterior and posterior nostril varies among the teleostean fishes (Kapoor and Ojha, 1972). The presence of nasal flaps in between the both nostrils is almost common when they are closely associated (Teichmann, 1954). The anterior and posterior nostril probably acts as an avenue for water ventilation through the olfactory rosette (Cox, 2008). The multilamellar 745 Journal of Research in Biology (2013) 3(1):

5 Plate - 3 Figure 3A - Schematic representation of Platycephalus scaber. Figure 3B - The diagram shows anterior and posterior nostrils of P. scaber situated at a distance from each other. Long nasal flap (FL) is also marked. Figure 3C - The olfactory apparatus of P. scaber is comprised of olfactory rosette (OLR), olfactory nerve (OLN), olfactory lobe (OL), cerebral hemisphere (CHS), optic lobe (OPL), cerebellum (CBL), medulla oblongata (MO), etc. Figure 3D - The circular olfactory rosette indicates central raphe (r) and two rows of lamella (l). The olfactory lamella is triangular in shape with prominent dorsal margin (dm), dorsal end (de) and proximal end (pe). olfactory rosette perhaps adopt several type of arrangement pattern (Holl, 1965). This lamellar arrangement may help in the particular sensitivity to certain components like amino acids, steroids, prostaglandins, etc. (Theisen et al., 1991). Anatomically the lamellar surface in S. commersonianus is much closer due to the short distance between anterior and posterior nostril than R. kanagurta and P. scaber. Therefore, the water soluble odorants may travel short distance to interact with comparatively greater olfactory lamellar surface of S. commersonianus. The water ventilation is assisted by the pumping mechanism of accessory nasal sacs (Theisen et al., 1991) and may provide the ability to sniff (Nevitt, 1991; Cox, 2008). R. kanagurta possesses well developed accessory nasal sacs but S. commersonianus and P. scaber has no accessory nasal sacs. The movement of jaws and its associated muscles are also very significant for the water ventilation (Nevitt, 1991). Accessory nasal sacs may be found in the olfactory organs of fishes with widely variable life styles and habitats, both marine and fresh water which are not confined to one particular situation (Cox, 2008). The olfactory nerve may convey the chemical cues during water ventilation to the brain (Hamdani and Døving, 2007). The olfactory information plays an important role in different behaviour of fish such as Journal of Research in Biology (2013) 3(1):

6 searching of foods, avoidance of predators, discrimination between individuals of the same and different, parental care, orientation in migration, etc. (Hara, 1971). The olfactory system of teleosts is highly a specialized structure for the recognition of various water soluble chemical cues, so this may serve as a biological model to monitor environmental health as well as specific meagerness of the pollutants. The xenotoxification of ocean especially the acidification may also impair the ability of olfactory discrimination of coastal and marine species (Munday et al., 2009). Thus, it is necessary to examine the effect of specific toxic agent at a subcellular level of olfactory structures in marine teleolsts. CONCLUSION This comparative anatomical study on the olfactory apparatus along with brain in three different marine teleost belonging to the diverse ecological habitat shows much structural variation according to the changing environment which may be significant for ecomorphology and evolutionary aspects of neurobiology (Kotrschal et al., 1998). However, the olfactory system of marine, estuarine and coastal or migratory species may experience rapid fluctuations of environmental inorganic ions (Hubbard et al., 2000), so it could be an interesting part to identify the cellular components that are involved in the ion regulation of the olfactory apparatus in these migratory teleosts. ACKNOWLEDGEMENTS Authors are thankful to the Head, Department of Zoology, Vidyasagar University, West Bengal, for providing the necessary laboratory facilities. REFERENCES Bone Q and Moore RH Biology of fishes, Third edition, Taylor and Francis Group, US and UK, Cox JPL Hydrodynamic aspects of fish olfaction. Journal of the Royal Society Interface, 5(23): Derivot JH Functional anatomy of the peripheral olfactory system of the African lungfish Protopterus annectens Owen: macroscopic, microscopic, and morphometric analysis. American Journal of Anatomy, 169(2): De SK and Sarkar SK Morphoanatomy of olfactory apparatus of Pseudapocryptes lanceolatus (Bloch and Schneider) Journal Environment and Ecology, 27(4): Døving KB The fish olfactory system: It s role in normal biology and in toxicological research. Proceedings of the Seventh International Symposium, Tallinn, Estonia Freitag J, Beck A, Ludwig, G, von Buchholtz L, Breer H On the origin of the olfactory receptor family: receptor genes of the jawless fish (Lampetra fluviatilis). Gene, 226(2): Hamdani EH, Døving KB The functional organization of the fish olfactory system. Prog Neurobiol, 82(2): Hansen A and Zeiske E The peripheral olfactory organ of the zebrafish, Danio rerio: an ultrastructural study. Chem Senses, 23: Hansen A, Rolen SH, Anderson KT, Morita Y, Caprio J, Finger, TE Correlation between olfactory receptor cell type and function in the channel catfish. J Neurosci., 23: Hansen A and Zielinski, BS Diversity in the olfactory epithelium of bony fishes: development, lamellar arrangement, sensory neuron cell types and transduction components. J Neurocytol., 34: Journal of Research in Biology (2013) 3(1):

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